1. Field of Invention
This invention relates to anchors and, more particularly, to anchors usable in all types of sea bottoms, including seaweed conditions and rock or coral bottoms.
2Description of the Prior Art
Anchors are used to moor or secure a vessel to the sea bed beneath the vessel. Anchors use a combination of weight and configuration to secure the vessel to the seabed. Thus, in addition to the weight of the anchor itself, the configuration of the anchor is designed to secure itself to the sea bottom, or to rocks, coral, etc., on the sea bottom.
Design limitations generally restrict the use of anchors according to sea bottom conditions. For example, heavy, opposing, dual arm type anchors have been used in seaweed conditions and on rock or coral bottoms. However, such anchors are less than effective in sand and mud conditions.
Danforth type anchors are generally effective in sand and mud bottoms, but they are relative ineffective in seaweed, rock, gravel, and coral bottoms.
Regardless of the particular configuration of an anchor, anchors generally have common elements, but the elements may be configured differently and they may be assembled in different manners. For example, an anchor includes a shank and one or more flukes. In some anchors, the flukes are secured on the outer ends of arms, and the shank is secured to the center of or between the arms.
Anchors typically also include a stock. Usually, the stock is generally perpendicular to the shank and remote from the arms and the flukes. However, in the Danforth type of anchor, the stock is adjacent to the flukes, and the shank is accordingly secured to the stock at the area of the fluke.
Some anchors do not use stocks. For example, anchors used on most relative large, contemporary ships do not use stocks. Such anchors include relatively large flukes that generally pivot from a central position as contact with the seabed is made. The flukes typically pivot in the direction of the pull on the anchor by the vessel, and the flukes then dig into the seabed.
U.S. Pat. No. 3,026,840 (Bevers) discloses an anchor of the Danforth type and utilizing a pair of pivoting flukes. A shank is secured between the flukes. The shank is a generally elongated U-shaped bar secured to a sleeve which pivots on a spindle joining the two flukes. An anchor chain is movable on the shank, and the use of the movable chain on the shank allows the relatively easy retrieval of the anchor from the seabed.
U.S. Pat. No. 3,782,318 (Hungerford) discloses another Danforth type anchor which utilizes cutting edges on a pair of closely adjacent flukes for cutting through seaweed, and the like, in order to penetrate to the bottom. The shank extends at an acute angle with respect to the plane of the flukes. A stock extends generally parallel to the plane of the flukes, and the shank is secured to the flukes adjacent to the stock. The stock is remote from the tips of the flukes.
U.S. Pat. No. 4,263,867 (Holmes) discloses a twin fluke type Danforth anchor in which the shank is somewhat similar to that of the Bevers '840 patent, discussed above. However, the shank in the Holmes patent is referred to as a hairpin shank and the arms of the hairpin are not parallel to each other.
The shanks of both the Bevers '840 patent and the Holmes '867 patent have an inherent problem, namely the fact that the shank elements tend to bend when substantial side pressures are placed on the anchor, as when the anchor is forced to turn to reset itself in the seabed.
U.S. Pat. No. 4,802,434 (Bruce) discloses an anchor with a shank connected directly to a main fluke in a generally "L" configuration. The main fluke includes two spaced apart toes, and there are auxiliary flukes extending outwardly from the main fluke and at angular orientations with respect to the main fluke. One of the primary benefits claimed for the Bruce '434 apparatus is that when the anchor lies inverted on a firm seabed, one of the auxiliary flukes will be in position for digging into the seabed when the anchor is pulled forwardly.
U.S. Pat. No. 4,827,863 (Scholz et al) discloses an anchor having a shank which pivots laterally with respect to a pair of flukes. The flukes are secured together at a mid point and extend downwardly and away from each other. The flukes come together at a central point or link, and the shank extends outwardly and forwardly above the flukes. The Scholz et al '863 apparatus is referred to as a plow anchor, designed to plow into the seabed.
As indicated above, the Danforth type anchors, or plow anchors, are relative effective in sand and mud bottoms, but are relatively ineffective in seaweed, rock, gravel, and coral bottoms. Moreover, extreme angular load conditions, such as imposed by rock or coral bottoms, cause problems with the Danforth type anchors. Likewise, seaweed and loose impediments also render such anchors relative ineffective, and in some cases even useless, until retrieved and cleaned.